1. Field of the Invention
This invention generally relates to a bicycle derailleur. More specifically, the present invention relates to a rear bicycle derailleur having an inner plate and tension pulley configured to prevent jamming of the derailleur when pushed into a moving bicycle wheel.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle derailleur.
Typically, a bicycle derailleur has a base member and a chain guide movably coupled to the base member via a linkage assembly. The base member is coupled to the frame of the bicycle. The chain guide is configured to move the chain laterally over a plurality of rear sprockets. A spring typically biases the chain guide to an innermost or outermost position relative to the sprockets. A Bowden-type control cable with an outer sheath and an inner wire is typically coupled to the derailleur and to a conventional shift control device.
The chain guide of a front derailleur includes a pair of shift plates arranged to move the chain laterally back and forth. The front derailleur is usually coupled to the seat tube of the frame. On the other, the rear derailleur is coupled to the rear triangle of the bicycle frame adjacent the rear wheel. The chain guide of the rear derailleur usually includes a pair of guide plates with a guide pulley and a tension pulley mounted between the guide plates. The chain is wrapped around both pulleys in an S-shaped manner between the guide plates in order to efficiently guide the chain to the appropriate sprocket during shifting and in order to appropriately tension the chain.
Due to the configuration of typical rear derailleurs, obstructions such as brush, debris, rocks, branches or the like sometimes contact them and cause the chain guide to move toward the rear wheel. If a sufficient force is applied to the rear derailleur, the inner chain guide plate and/or the tension pulley can be pushed into the rear wheel. In particular, if a sufficient force is applied to the chain guide by an obstruction, the inner chain guide plate and/or the tension pulley can contact the spokes of the rear wheel. Such contact can jam the rear wheel and/or the rear derailleur, resulting in decreased riding/shifting performance.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle derailleur. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.